Tow-coil PI MD.

[Orbit]

Hi Eric I'm glad you're ok that you are back with us !

[RKC]

Hi Rob, It is quite an easy mod to run two coils, but is does mean a mod to the circuit board. Basically it is to separate the TX from the RX input and then take the RX to a separate coil connector. Each coil has to have its own damping resistor. This type of system, depending on coil separation, has poor response to small targets but does reduce the effect of mineralised ground considerably. Two 15in coils would be do-able. The RX can have more turns and a higher inductance to enhance the received signal.
One problem is that there is no space on the Aquapulse for another connector.

Eric.

G'day Eric,

Back after I made the original post in 2009 I came to the conclusion that it would be "quite an easy mod to run two coils", on my Aquapulse. And a start was was attempted back then, with the assistance of an electrical guy I met on this forum, for him to do the electrical "stuff", so it could be converted to run two coils. But after the detector had been sent back and forth over many months, in the end nothing came of it. Its a long time ago to remember the exact details, but I do remember the attempts were abandoned. I would have liked to have come up with a two-coil PI detector, and I sure could have used one over the years since 2009. I'm useless myself with any altering of MD electrics and have made such a mess of detectors I am not game to do any modifications myself any more. I once even foolishly attempted to alter one of your GQSS detectors to a two-coil MD.

The reason I need a two-coil detector is to detect in areas of heavy vegetation. As I mentioned in my first post in this thread I tried a 1 meter coil on my Aquapulse (from a Bulgarian detector I had bought before the Aquapiulse) and it worked very well to give me the depth I needed, but, it was not maneuverable in thick scrub. I tried the coil in a rectangular shape which was much easier to get through the vegetation, but it did not give me anywhere near the depth I needed. A typical VLF two-coil MD is easily maneuverable in thick vegetation, but does not get the depth I need on the targets I'm after (I found they are only of any use if expecting to find gold nuggets the size of a car). The gold is not particularly deep in the ground, but there is at least 2 feet of thick vegetation over all the ground. If I could remove the vegetation I could use a fairly conventional PI detector with a large round coil and have plenty of success. But its not practical to remove native vegetation ... and highly illegal in Godzone!

Heavily mineralized ground is not an issue for me as here in New Zealand the ground is extremely quiet. Back in the early 2000s there were discussions on the Internet MD forums about whether the ground in New Zealand is HOT like across the ditch in Australia (thus necessitating, or not, the use of expensive Minelab detectors ... the Minelab dealers were telling the Kiwi punters the ground was HOT http://www.finders.com.au/forum/viewtopic.php?t=2430 ) and we came to the conclusion the ground in Australia, compared to New Zealand, is the exact opposite. We theorized it must have had something to do with the geological ages of each country, with Australia one of the oldest continents, and New Zealand the relatively newest country. Australia being so geologically old has been subject to erosion over millions of years that left behind the (iron?) mineralisation on ground that had weathered away from great heights. The exact opposite happened in New Zealand with a 'geologically' new upward thrust from volcanic action. Out of interest, I once tried my Aquapulse in an Australian gold field, and to it, all the ground was all one great massive target (no surprises there).

Since 2009 when I first made the post requesting information on two-coil detectors I have learnt a great deal more about the type of detectors I need to use in New Zealand. And to help me, MD technology has improved considerably since then, along with an easy availability of MD technology, bought from anywhere in the world. And I think I have finally solved my problem of getting a suitable MD to use in the thick vegetation in New Zealands gold laden West Coast forests (although there is still some field-work to be done).

Regards,
Rob (RKC)